The invention relates to a fastening element, in particular to a fastening element, with at least one nut and with at least one thrust washer, wherein the nut has at least one interior space with an internal thread, an abutment surface, and a snap edge that encloses the abutment surface. The snap edge includes a radially inwardly projecting nose edge that preferably runs radially completely around the circumference of the nut as does a chamber formed between the abutment surface, the snap edge and the nose edge. The thrust washer has an interior recess.
Such fastening elements, which are composed of at least two parts, nut and thrust washer, are used in the prior art for axle central screw couplings on commercial vehicles, for example. Examples of alternative names for the thrust washer are pressure disc, spring collar, locking washer or, generally, plate.
A three-part fastening element in which a thrust ring is connected in a captive manner via a flanged and circumferential clamp to the nut is disclosed, for example, by German utility model patent document no. DE 88 13 513 U1. The thrust ring has a spherical calotte—(i.e., skullcap) shaped underside.
A two-part fastening means in which the thrust washer is held by the nut in a rotatable and captive manner via special retaining lugs is disclosed by European patent document no. EP 1 577 571 B1. However, the manufacture of the retaining lugs and bending them over into the cavity of the nut is costly.
In the function as the axle center nut in commercial vehicles, one-piece all-metal locknuts are particularly used to line up the wheel bearing and fasten the wheel hub. In this application, it is generally necessary to dispose a thrust washer between wheel bearing and locknut that is secured against rotation in the fastened state and ensures the self-retention function of the axle center nut during load-cycle changes.
When tightening the locknut on a bolt across from a mounting face—e.g., the wheel hub—torques and biasing forces must be applied which depend on the cooperation between the nut and the bolt as well as of the head seat of the mounting face. In the axle central screw couplings of the prior art, the head seat is formed by the disc, which is secured against rotation, particularly by positive mechanical engagement. As a result, a disc that is not present or is improperly positions can influence and distort the variables to be monitored during bolting. This, in turn, can lead to substantial safety risks.
It is therefore an object of the invention to provide a fastening element that enables maximally simple assembly, prevents the thrust washer from being forgotten, and ensures secure positioning of the thrust washer.
The fastening element according to the invention is first and substantially characterized in that the thrust washer has at least one flanged portion with an outside diameter and one cylindrical portion with an outside diameter, that the outside diameter of the flanged portion is greater than the outside diameter of the cylindrical portion, and that the flanged portion, the cylindrical portion, the snap edge and the nose edge are coordinated such with one another and the nose edge projects so far into the interior of the nut that the nose edge and the snap edge enclose the flanged portion at least partially.
The thrust washer of the fastening element according to the invention has at least two portions that differ from one another at least through their outside diameter. The flanged portion has a larger outside diameter than the cylindrical portion.
In one embodiment, the cylindrical portion has a cylindrical outer surface with a circular base area. The cylinder itself is a hollow cylinder due to the central opening for the bolt. In a supplementary or alternative embodiment, the flanged portion has a cylindrical outer surface with a circular base area.
In order to retain the thrust washer so as not to be lost, the flanged portion, the cylindrical portion, the snap edge, and the nose edge are coordinated such with one another and the nose edge projects so far into the interior of the nut that the nose edge and the snap edge enclose the flanged portion at least partially. As a result of the nose edge, which is inwardly aligned, the thrust washer is particularly secured against falling out of the chamber of the nut.
In one embodiment, the snap edge is an edge that completely encloses the abutment surface radially. In an alternative embodiment, the snap edge is not completely closed but rather has discontinuities, so that in this embodiment the abutment surface is also enclosed radially only in part by the snap edge.
In one embodiment, the nose edge is embodied particularly so as to run around circumferentially and thus form an annular edge or a circumferential edge on which the thrust washer rests. In one embodiment, the flanged portion rests particularly on the nose edge and the cylindrical portion is enclosed radially by the nose edge. There is preferably a radial clearance at least between the cylindrical portion and the nose edge.
One embodiment particularly involves a two-part fastening element which, as a result of the incorporation of the thrust washer during manufacture and the resulting captive fastening, is to be used as a complete component. This simplifies handling by the user of the fastening element.
In one embodiment, the flanged portion and the snap edge are coordinated with one another such that the snap edge encloses the flanged portion with a gap, preferably a radially circumferential gap. In one embodiment, a clearance which enables rotation between nut and thrust washer exists between the flanged portion, which is located within the chamber of the nut, and the snap edge. There is therefore a movable connection between nut and thrust washer which also enables consideration to be given to manufacturing tolerances.
As regards the geometry of the thrust washer, and therefore also indirectly with respect to the geometry of the nut, a provision is made in one embodiment that the flanged portion and/or the cylindrical portion and/or the thrust washer are embodied so as to be rotationally symmetrical about a longitudinal axis.
In one variant, the thrust washer is a part that consists of two hollow cylindrical portions, each with a circular base surface, the outside diameters of which differ from one another. The heights of the portions—that is, of the flanged and cylindrical portions—depends on the height of the snap edge and on the amount by which the thrust washer is to project over the nut.
The preceding embodiment is achieved, for example, with a design in which the thrust washer is embodied as a substantially massive component. In one embodiment, the thrust washer is produced as a turned part by stock removal at least in one production step and, in an alternative embodiment, it is produced using a suitable non-cutting shaping method.
In one embodiment, the two outer axial base areas of the thrust washer are each planar or flat. In one embodiment, at least the outer side of the flanged or of the cylindrical portion is planar and free of convexities. In one embodiment, at least one base area is not planar but rather has at least one convexity or recess.
The thrust washer is preferably held by the nose edge and is thus captively connected to the nut. The nut itself is particularly a massive component that is made of a metal, particularly steel.
In order to connect the thrust washer with the nut to the fastening element, one embodiment makes a provision that the nose edge and/or snap edge of the nut can be widened in a substantially elastic manner. For manufacturing, the thrust washer is therefore introduced into the chamber of the nut such that the latter widens substantially slightly elastically, thus permitting the introduction of the thrust washer. The material and particularly also the geometric dimensions of the nut particularly with respect to the snap edge and the nose edge must be selected accordingly.
As a result of the elastic widening, the snap edge and/or the nose edge returns to the original position or geometric shape after the introduction of the thrust washer and then captively secures the thrust washer.
To simplify the introduction of the thrust washer into the chamber of the nut, the two following embodiments are particularly provided and can be implemented together or each individually.
In one embodiment the nose edge tapers axially in the direction facing away from the abutment surface such that a radially circumferential chamfer is produced on the radially interior side of the nose edge. In this embodiment, the nose edge thus has such a taper on the side facing toward the thrust washer that the nose edge is narrower toward the outside—that is, in the direction facing away from the abutment surface of the nut—or, phrased the other way around, that the surface of the nose edge on which the thrust washer rests with its flanged portion projects radially farther into the interior of the nut than the axially outer end of the nose edge. This also results in targeted weakening of the material, which facilitates the elastic widening for the introduction of the thrust washer.
In an alternative embodiment at least one radially circumferential taper is provided on an end of the flanged portion of the thrust washer facing away from the cylindrical portion. In this embodiment, the flanged portion does not have a base area with a rectangular edge, for example, but rather a taper is provided that renders the radius of the base area of the flanged portion smaller in this direction than the outside diameter of the cylindrical flanged portion.
In another embodiment, particularly when the fastening element is used as an axle central screw coupling, micromovements between the bolt and the fastening element and loosening from the bolt, which may occur as a result of load-cycle changes, are inhibited by the thrust washer being prevented from rotating in relation to the bolt by virtue of its shape, such as by the provision of at least one projection projecting into the interior recess of the thrust washer.
In one embodiment, the at least one projection projecting into the interior recess of the thrust washer is provided on an end of the cylindrical portion facing away from the flanged portion. In another embodiment, at least two projections projecting into the interior recess of the thrust washer are provided. The at least two projections are arranged in one embodiment so as to lie substantially diametrically opposite one another.
The projection or projections are intended to prevent rotation of the thrust washer in relation to the bolt in the tightened or fastened state. In one embodiment, the projections are or the projection is present substantially along the entire height of the interior recess of the thrust washer. In another variant, the thrust washer is spring-loaded.
Preferably, the spring-loaded thrust washer may be introduced into the chamber of the nut such that the thrust washer is biased when it is fastened on a bolt. The nut and the thrust washer must be appropriately designed and coordinated with one another.
The further introduction of the thrust washer into the chamber of the nut takes place in the spring-loaded thrust washer, upon fastening of the fastening element onto a bolt. During fastening, the thrust washer is pressed flat between nut and bearing surface, and a bias builds up that results from the fact that the spring-loaded thrust washer would like to return to its initial geometry.
A provision may be made in one embodiment that, in the state without bias—that is, in the relaxed initial position—the thrust washer spans an imaginary base area with a raised area. Since the thrust washer has a central recess (for the bolt), the imaginary base area results particularly from the fact that the empty interior is imaginarily connected to the surrounding areas of the thrust washer. The geometry and shape of the thrust washer thus brings about an arching of the thrust washer. This arching points out of the nut against the abutment surface of the nut (i.e., out of the nut) or in the direction of the abutment surface and thus quasi into the nut.
In one embodiment, only one raised area is provided. In another embodiment, the one raised area lies substantially on the longitudinal axis of the thrust washer. A raised convexity of the thrust washer preferably lies on the longitudinal axis of the thrust washer. If the thrust washer is embodied so as to be rotationally symmetrical, the raised area lies on the longitudinal axis around which the thrust washer is rotationally symmetrical. In this embodiment, if the fastening element is tightened around a bolt against a surface (e.g., a wheel hub), then when the thrust washer projects outwardly in the home position in the direction facing away from the abutment surface, the thrust washer is pressed axially in the direction of the abutment surface of the nut. As a result, the cylindrical portion is preferably guided in the direction of the snap edge. The bias is produced here through the “pressing-flat” of the thrust washer, which would like to return to the initial position with raised area.
Another embodiment makes a provision that at least one retaining element is present at a free end of the nut. The purpose of the retaining element is to secure the nut against rotation on a bolt thread on which the fastening element overall is to be fastened. The free end of the nut lies across from the end of the nut having the abutment surface. The retaining element is a retaining element that is based on friction in the thread, such as a clamping element or clamping segment, for example, whose threaded region is sloped at a predeterminable angle of inclination in the direction of the longitudinal axis of the nut and thus reaches into the interior of the nut. Such a retaining element is known, for example, from the applicant's ENKO nuts.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.